Once again, science fiction has taken a philosophical turn. Both "Star Trek" and "The Black Hole" are full of interstellar escapades and outer-space effects straight from "Star Wars." Yet neither of the new pictures is content to rest with the usual cute robots and "space opera" heroics. After an hour or so of mindless fun, they veer deliberately toward the kind of "mysterious" meditations that distinguished "2001: A Space Odyssey," the grandaddy of all the SF films of the 1970s.

Of the two, "Star Trek" is most successful -- though probably not successful enough to recoup easily its enormous cost, which has been estimated at some $40 million.

Naturally, the characters -- and their home-away-from-earth, the starship Enterprise -- come directly from the unkillable "Star Trek" TV series. At the beginning of the movie there are some shenanigans with aliens and ray guns. Then we and the crew get down to business, voyaging to an enigmatic cloud in deep space, which seems to be shrouding some kind of weird but intelligent life form.

For the first hour or so, "Star Trek" is a bore, albeit an expensive one. The visual effects are old hat, and there are far too many shots of the Enterprise and her passengers going about their cosmic affairs. Realistic or not, such tricks no longer carry much of a premium in fantasyland.

As the movie enters its second hour, however, it starts to pick up. We get closer to that peculiar cloud, and then we actually penetrate it, and the story takes on an aura of genuine mystery -- a sense that something grand and special is going on. For a while, there are echoes of Stanislaw Lem's "Solaris," as the spacemen theorize that they have discovered a unique entity among the flotsam and jetsam of space. And then comes the payoff of the movie -- the revelation of just what the cloud contains. It's not a totally original idea, but it's a good one, compounded of ingenuity and good humor. It is followed by a delirious climax that makes up in ostentation what it lacks in sense.

Even by today's sci-fi standards, "Star Trek" is surprisingly devoid of old- fashioned "human" values. William Shatner, Leonard Nimoy, and the rest of the cast have little to do but hang around the control room, push buttons, and mimic a few basic emotions. The dialogue is stiff and the action seems preprogrammed every step of the way. It's as if the director, veteran fantasist Robert Wise, had typed the whole picture into a computer terminal, then sat back and waited for a celluloid printout.

But that's all the more reason to feel a bit of excitement -- or maybe it's just relief -- when the Enterprise begins to penetrate that ominous nebula, which remains cloaked in obscurity until the very last moment, except for bizarre clues from a robotic emissary. As dull as it is to watch, "Star Trek" at least possesses a measure of intellectual pizzazz: not enough to provoke thought and discussion, exactly, but more than many "Star Wars" imitators have bothered to give us.

"The Black Hole" also has ambitions toward philosophical grandeur. Tired of its reputation for unalloyed kiddie fare, Walt Disney Productions has spared no effort to make this its most lavish movie ever -- with a portentous screenplay, a big-name cast, and an unprecedented budget of some $17 million.

Alas, the results fall way short. Until the last part of the picture, the plot is trite -- all about a likeable space crew who battle a wicked scientist and his army of humanoids. The villain is a spacey rehash of Captain Nemo from "20,000 Leagues Under the Sea," and the humor is provided by a pair of androids shamelessly borrowed from "Star Wars."

Even the camera tricks often seem half-hearted -- and in at least one scene, the wires holding up a "weightless" object are as visible as the galaxies hanging outside the spaceship window! Designer Peter Ellenshaw, an old master if ever there was one, has not been well served by his technicians. Only a few effects (mostly near the end) are gratifyingly original or spectacular.

Things get a bit more interesting in the final scenes, after the derring-do has been dispensed with. At long last we plunge into the black hole itself, and suddenly the film becomes a mad mixture of "2001" and Dante's "Divine comedy." Unfortunately, it doesn't make a bit of sense -- not the intuitive sense of " 2001," or the allegorical sense of Dante, or the horse sense of any good movie-movie. A space warp and a time warp are fine things, in their place, but a plot warp is a lot trickier to navigate. "The Black Hole" makes a game try, but crashlands someplace on the far side of paradise.